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	$116.28	11.660%	$129.8382	$129.84	$129.85	$129.80
Purchase #2	$174.94	8.281%	$189.4268	$189.43	$189.45	$189.40
Purchase #3	$98.32	11.846%	$109.967	$109.97	$109.95	$110.00
Purchase #4	$79.54	7.764%	$85.7155	$85.72	$85.70	$85.70
Purchase #5	$214.68	4.199%	$223.6944	$223.69	$223.70	$223.70
Purchase #6	$103.72	5.121%	$109.0315	$109.03	$109.05	$109.00
Purchase #7	$231.95	10.545%	$256.4091	$256.41	$256.40	$256.40
7 purchase totals =	$1,019.43		$1,104.0825	$1,104.09	$1,104.10	$1,104.00