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	$92.33	12.547%	$103.9146	$103.91	$103.90	$103.90
Purchase #2	$226.52	10.510%	$250.3273	$250.33	$250.35	$250.30
Purchase #3	$228.58	9.476%	$250.2402	$250.24	$250.25	$250.20
Purchase #4	$103.86	9.213%	$113.4286	$113.43	$113.45	$113.40
Purchase #5	$158.44	13.137%	$179.2543	$179.25	$179.25	$179.30
Purchase #6	$55.80	6.377%	$59.3584	$59.36	$59.35	$59.40
Purchase #7	$60.42	13.216%	$68.4051	$68.41	$68.40	$68.40
7 purchase totals =	$925.95		$1,024.9285	$1,024.93	$1,024.95	$1,024.90