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	$179.59	8.426%	$194.7223	$194.72	$194.70	$194.70
Purchase #2	$48.75	9.494%	$53.3783	$53.38	$53.40	$53.40
Purchase #3	$54.72	11.182%	$60.8388	$60.84	$60.85	$60.80
Purchase #4	$103.56	5.642%	$109.4029	$109.40	$109.40	$109.40
Purchase #5	$29.70	8.450%	$32.2097	$32.21	$32.20	$32.20
Purchase #6	$213.27	3.870%	$221.5235	$221.52	$221.50	$221.50
Purchase #7	$99.68	9.404%	$109.0539	$109.05	$109.05	$109.10
7 purchase totals =	$729.27		$781.1294	$781.12	$781.10	$781.10