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	$36.43	3.167%	$37.5837	$37.58	$37.60	$37.60
Purchase #2	$129.58	11.568%	$144.5698	$144.57	$144.55	$144.60
Purchase #3	$12.82	6.642%	$13.6715	$13.67	$13.65	$13.70
Purchase #4	$29.86	6.783%	$31.8854	$31.89	$31.90	$31.90
Purchase #5	$235.38	4.133%	$245.1083	$245.11	$245.10	$245.10
Purchase #6	$201.48	7.263%	$216.1135	$216.11	$216.10	$216.10
Purchase #7	$43.72	4.218%	$45.5641	$45.56	$45.55	$45.60
7 purchase totals =	$689.27		$734.4963	$734.49	$734.45	$734.60