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	$34.55	9.299%	$37.7628	$37.76	$37.75	$37.80
Purchase #2	$89.79	4.107%	$93.4777	$93.48	$93.50	$93.50
Purchase #3	$101.55	4.688%	$106.3107	$106.31	$106.30	$106.30
Purchase #4	$42.50	6.171%	$45.1227	$45.12	$45.10	$45.10
Purchase #5	$73.27	12.850%	$82.6852	$82.69	$82.70	$82.70
Purchase #6	$96.45	10.781%	$106.8483	$106.85	$106.85	$106.80
Purchase #7	$198.88	6.321%	$211.4512	$211.45	$211.45	$211.50
7 purchase totals =	$636.99		$683.6586	$683.66	$683.65	$683.70