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	$174.87	12.586%	$196.8791	$196.88	$196.90	$196.90
Purchase #2	$104.87	10.182%	$115.5479	$115.55	$115.55	$115.50
Purchase #3	$34.35	8.403%	$37.2364	$37.24	$37.25	$37.20
Purchase #4	$27.26	7.229%	$29.2306	$29.23	$29.25	$29.20
Purchase #5	$129.67	12.746%	$146.1977	$146.20	$146.20	$146.20
Purchase #6	$148.72	10.817%	$164.807	$164.81	$164.80	$164.80
Purchase #7	$83.41	4.133%	$86.8573	$86.86	$86.85	$86.90
7 purchase totals =	$703.15		$776.7560	$776.77	$776.80	$776.70