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	$66.84	8.511%	$72.5288	$72.53	$72.55	$72.50
Purchase #2	$191.53	10.221%	$211.1063	$211.11	$211.10	$211.10
Purchase #3	$131.74	6.656%	$140.5086	$140.51	$140.50	$140.50
Purchase #4	$124.92	4.731%	$130.83	$130.83	$130.85	$130.80
Purchase #5	$116.68	4.461%	$121.8851	$121.89	$121.90	$121.90
Purchase #6	$218.82	5.331%	$230.4853	$230.49	$230.50	$230.50
Purchase #7	$134.96	5.865%	$142.8754	$142.88	$142.90	$142.90
7 purchase totals =	$985.49		$1,050.2195	$1,050.24	$1,050.30	$1,050.20