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	$105.64	7.722%	$113.7975	$113.80	$113.80	$113.80
Purchase #2	$52.60	11.422%	$58.608	$58.61	$58.60	$58.60
Purchase #3	$56.49	9.362%	$61.7786	$61.78	$61.80	$61.80
Purchase #4	$83.76	6.785%	$89.4431	$89.44	$89.45	$89.40
Purchase #5	$132.97	6.673%	$141.8431	$141.84	$141.85	$141.80
Purchase #6	$165.30	3.523%	$171.1235	$171.12	$171.10	$171.10
Purchase #7	$166.42	4.474%	$173.8656	$173.87	$173.85	$173.90
7 purchase totals =	$763.18		$810.4594	$810.46	$810.45	$810.40