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	$199.73	7.217%	$214.1445	$214.14	$214.15	$214.10
Purchase #2	$216.95	5.276%	$228.3963	$228.40	$228.40	$228.40
Purchase #3	$47.55	4.666%	$49.7687	$49.77	$49.75	$49.80
Purchase #4	$208.31	7.689%	$224.327	$224.33	$224.35	$224.30
Purchase #5	$85.92	4.617%	$89.8869	$89.89	$89.90	$89.90
Purchase #6	$61.86	9.665%	$67.8388	$67.84	$67.85	$67.80
Purchase #7	$132.89	6.416%	$141.4162	$141.42	$141.40	$141.40
7 purchase totals =	$953.21		$1,015.7784	$1,015.79	$1,015.80	$1,015.70