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	$82.54	11.332%	$91.8934	$91.89	$91.90	$91.90
Purchase #2	$87.39	8.820%	$95.0978	$95.10	$95.10	$95.10
Purchase #3	$47.76	11.451%	$53.229	$53.23	$53.25	$53.20
Purchase #4	$101.43	9.816%	$111.3864	$111.39	$111.40	$111.40
Purchase #5	$49.46	6.744%	$52.7956	$52.80	$52.80	$52.80
Purchase #6	$165.49	4.572%	$173.0562	$173.06	$173.05	$173.10
Purchase #7	$80.32	8.361%	$87.0356	$87.04	$87.05	$87.00
7 purchase totals =	$614.39		$664.4940	$664.51	$664.55	$664.50