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	$85.59	3.661%	$88.7234	$88.72	$88.70	$88.70
Purchase #2	$86.71	10.656%	$95.9498	$95.95	$95.95	$95.90
Purchase #3	$154.43	7.532%	$166.0617	$166.06	$166.05	$166.10
Purchase #4	$30.95	8.247%	$33.5024	$33.50	$33.50	$33.50
Purchase #5	$8.48	3.225%	$8.7535	$8.75	$8.75	$8.80
Purchase #6	$84.91	4.813%	$88.9967	$89.00	$89.00	$89.00
Purchase #7	$160.31	4.111%	$166.9003	$166.90	$166.90	$166.90
7 purchase totals =	$611.38		$648.8878	$648.88	$648.85	$648.90