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	$237.91	6.575%	$253.5526	$253.55	$253.55	$253.60
Purchase #2	$168.33	13.867%	$191.6723	$191.67	$191.65	$191.70
Purchase #3	$64.80	11.194%	$72.0537	$72.05	$72.05	$72.10
Purchase #4	$176.85	4.328%	$184.5041	$184.50	$184.50	$184.50
Purchase #5	$156.64	3.588%	$162.2602	$162.26	$162.25	$162.30
Purchase #6	$229.42	12.148%	$257.2899	$257.29	$257.30	$257.30
Purchase #7	$247.86	12.790%	$279.5613	$279.56	$279.55	$279.60
7 purchase totals =	$1,281.81		$1,400.8941	$1,400.88	$1,400.85	$1,401.10