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	$176.70	7.145%	$189.3252	$189.33	$189.35	$189.30
Purchase #2	$33.73	7.501%	$36.2601	$36.26	$36.25	$36.30
Purchase #3	$204.94	8.403%	$222.1611	$222.16	$222.15	$222.20
Purchase #4	$127.75	11.783%	$142.8028	$142.80	$142.80	$142.80
Purchase #5	$45.73	12.435%	$51.4165	$51.42	$51.40	$51.40
Purchase #6	$199.28	12.123%	$223.4387	$223.44	$223.45	$223.40
Purchase #7	$54.61	8.142%	$59.0563	$59.06	$59.05	$59.10
7 purchase totals =	$842.74		$924.4607	$924.47	$924.45	$924.50