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	$53.82	13.498%	$61.0846	$61.08	$61.10	$61.10
Purchase #2	$65.56	9.474%	$71.7712	$71.77	$71.75	$71.80
Purchase #3	$71.88	11.183%	$79.9183	$79.92	$79.90	$79.90
Purchase #4	$39.38	8.205%	$42.6111	$42.61	$42.60	$42.60
Purchase #5	$167.26	10.805%	$185.3324	$185.33	$185.35	$185.30
Purchase #6	$165.80	3.381%	$171.4057	$171.41	$171.40	$171.40
Purchase #7	$100.97	10.560%	$111.6324	$111.63	$111.65	$111.60
7 purchase totals =	$664.67		$723.7557	$723.75	$723.75	$723.70