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	$79.49	3.292%	$82.1068	$82.11	$82.10	$82.10
Purchase #2	$36.31	7.629%	$39.0801	$39.08	$39.10	$39.10
Purchase #3	$162.68	10.574%	$179.8818	$179.88	$179.90	$179.90
Purchase #4	$221.79	12.331%	$249.1389	$249.14	$249.15	$249.10
Purchase #5	$146.30	3.644%	$151.6312	$151.63	$151.65	$151.60
Purchase #6	$213.51	4.686%	$223.5151	$223.52	$223.50	$223.50
Purchase #7	$114.54	9.615%	$125.553	$125.55	$125.55	$125.60
7 purchase totals =	$974.62		$1,050.9069	$1,050.91	$1,050.95	$1,050.90