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	$192.69	5.578%	$203.4382	$203.44	$203.45	$203.40
Purchase #2	$63.36	7.142%	$67.8852	$67.89	$67.90	$67.90
Purchase #3	$43.59	8.666%	$47.3675	$47.37	$47.35	$47.40
Purchase #4	$38.95	11.188%	$43.3077	$43.31	$43.30	$43.30
Purchase #5	$196.50	13.639%	$223.3006	$223.30	$223.30	$223.30
Purchase #6	$95.90	10.771%	$106.2294	$106.23	$106.25	$106.20
Purchase #7	$147.78	5.685%	$156.1813	$156.18	$156.20	$156.20
7 purchase totals =	$778.77		$847.7099	$847.72	$847.75	$847.70