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	$87.96	3.502%	$91.0404	$91.04	$91.05	$91.00
Purchase #2	$40.57	13.583%	$46.0806	$46.08	$46.10	$46.10
Purchase #3	$128.46	10.587%	$142.0601	$142.06	$142.05	$142.10
Purchase #4	$116.77	10.389%	$128.9012	$128.90	$128.90	$128.90
Purchase #5	$76.76	7.243%	$82.3197	$82.32	$82.30	$82.30
Purchase #6	$249.55	5.608%	$263.5448	$263.54	$263.55	$263.50
Purchase #7	$245.88	9.313%	$268.7788	$268.78	$268.80	$268.80
7 purchase totals =	$945.95		$1,022.7256	$1,022.72	$1,022.75	$1,022.70