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	$92.38	7.252%	$99.0794	$99.08	$99.10	$99.10
Purchase #2	$139.36	9.247%	$152.2466	$152.25	$152.25	$152.20
Purchase #3	$209.54	5.358%	$220.7672	$220.77	$220.75	$220.80
Purchase #4	$51.25	4.471%	$53.5414	$53.54	$53.55	$53.50
Purchase #5	$121.61	12.225%	$136.4768	$136.48	$136.50	$136.50
Purchase #6	$216.28	6.336%	$229.9835	$229.98	$230.00	$230.00
Purchase #7	$247.48	9.421%	$270.7951	$270.80	$270.80	$270.80
7 purchase totals =	$1,077.90		$1,162.8900	$1,162.90	$1,162.95	$1,162.90