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	$68.73	4.469%	$71.8015	$71.80	$71.80	$71.80
Purchase #2	$208.73	6.387%	$222.0616	$222.06	$222.05	$222.10
Purchase #3	$105.99	6.430%	$112.8052	$112.81	$112.80	$112.80
Purchase #4	$89.80	7.333%	$96.385	$96.39	$96.40	$96.40
Purchase #5	$149.97	13.428%	$170.108	$170.11	$170.10	$170.10
Purchase #6	$174.89	13.476%	$198.4582	$198.46	$198.45	$198.50
Purchase #7	$209.42	11.465%	$233.43	$233.43	$233.45	$233.40
7 purchase totals =	$1,007.53		$1,105.0495	$1,105.06	$1,105.05	$1,105.10