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	$53.32	10.740%	$59.0466	$59.05	$59.05	$59.00
Purchase #2	$36.72	6.303%	$39.0345	$39.03	$39.05	$39.00
Purchase #3	$108.77	4.557%	$113.7266	$113.73	$113.75	$113.70
Purchase #4	$58.53	5.296%	$61.6297	$61.63	$61.65	$61.60
Purchase #5	$32.32	10.587%	$35.7417	$35.74	$35.75	$35.70
Purchase #6	$162.87	5.813%	$172.3376	$172.34	$172.35	$172.30
Purchase #7	$50.42	10.644%	$55.7867	$55.79	$55.80	$55.80
7 purchase totals =	$502.95		$537.3034	$537.31	$537.40	$537.10