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	$35.48	4.364%	$37.0283	$37.03	$37.05	$37.00
Purchase #2	$89.63	11.130%	$99.6058	$99.61	$99.60	$99.60
Purchase #3	$168.56	12.654%	$189.8896	$189.89	$189.90	$189.90
Purchase #4	$219.60	11.408%	$244.652	$244.65	$244.65	$244.70
Purchase #5	$179.49	3.638%	$186.0198	$186.02	$186.00	$186.00
Purchase #6	$93.60	4.251%	$97.5789	$97.58	$97.60	$97.60
Purchase #7	$171.92	8.284%	$186.1619	$186.16	$186.15	$186.20
7 purchase totals =	$958.28		$1,040.9363	$1,040.94	$1,040.95	$1,041.00