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	$57.59	3.769%	$59.7606	$59.76	$59.75	$59.80
Purchase #2	$92.83	11.563%	$103.5639	$103.56	$103.55	$103.60
Purchase #3	$214.34	7.680%	$230.8013	$230.80	$230.80	$230.80
Purchase #4	$216.92	3.216%	$223.8961	$223.90	$223.90	$223.90
Purchase #5	$32.97	13.268%	$37.3445	$37.34	$37.35	$37.30
Purchase #6	$216.87	5.282%	$228.3251	$228.33	$228.35	$228.30
Purchase #7	$110.52	13.703%	$125.6646	$125.66	$125.65	$125.70
7 purchase totals =	$942.04		$1,009.3561	$1,009.35	$1,009.35	$1,009.40