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	$218.83	5.359%	$230.5571	$230.56	$230.55	$230.60
Purchase #2	$110.52	11.340%	$123.053	$123.05	$123.05	$123.10
Purchase #3	$165.32	10.361%	$182.4488	$182.45	$182.45	$182.40
Purchase #4	$172.49	10.796%	$191.112	$191.11	$191.10	$191.10
Purchase #5	$59.91	11.413%	$66.7475	$66.75	$66.75	$66.70
Purchase #6	$238.41	13.713%	$271.1032	$271.10	$271.10	$271.10
Purchase #7	$109.39	10.469%	$120.842	$120.84	$120.85	$120.80
7 purchase totals =	$1,074.87		$1,185.8636	$1,185.86	$1,185.85	$1,185.80