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	$64.56	9.814%	$70.8959	$70.90	$70.90	$70.90
Purchase #2	$61.35	11.868%	$68.631	$68.63	$68.65	$68.60
Purchase #3	$178.71	3.582%	$185.1114	$185.11	$185.10	$185.10
Purchase #4	$219.61	10.289%	$242.2057	$242.21	$242.20	$242.20
Purchase #5	$84.66	6.263%	$89.9623	$89.96	$89.95	$90.00
Purchase #6	$174.62	9.766%	$191.6734	$191.67	$191.65	$191.70
Purchase #7	$96.30	9.440%	$105.3907	$105.39	$105.40	$105.40
7 purchase totals =	$879.81		$953.8704	$953.87	$953.85	$953.90