Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$107.72	3.313%	$111.2888	$111.29	$111.30	$111.30
Purchase #2	$136.36	10.817%	$151.1101	$151.11	$151.10	$151.10
Purchase #3	$127.71	4.813%	$133.8567	$133.86	$133.85	$133.90
Purchase #4	$193.80	3.116%	$199.8388	$199.84	$199.85	$199.80
Purchase #5	$156.67	7.462%	$168.3607	$168.36	$168.35	$168.40
Purchase #6	$110.98	4.374%	$115.8343	$115.83	$115.85	$115.80
Purchase #7	$215.35	7.839%	$232.2313	$232.23	$232.25	$232.20
7 purchase totals =	$1,048.59		$1,112.5207	$1,112.52	$1,112.55	$1,112.50