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	$194.84	5.388%	$205.338	$205.34	$205.35	$205.30
Purchase #2	$250.82	9.112%	$273.6747	$273.67	$273.65	$273.70
Purchase #3	$141.78	5.606%	$149.7282	$149.73	$149.75	$149.70
Purchase #4	$181.51	5.662%	$191.7871	$191.79	$191.80	$191.80
Purchase #5	$50.72	8.403%	$54.982	$54.98	$55.00	$55.00
Purchase #6	$102.96	8.728%	$111.9463	$111.95	$111.95	$111.90
Purchase #7	$134.72	4.130%	$140.2839	$140.28	$140.30	$140.30
7 purchase totals =	$1,057.35		$1,127.7402	$1,127.74	$1,127.80	$1,127.70