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	$166.98	4.734%	$174.8848	$174.88	$174.90	$174.90
Purchase #2	$36.68	9.722%	$40.246	$40.25	$40.25	$40.20
Purchase #3	$37.73	9.633%	$41.3645	$41.36	$41.35	$41.40
Purchase #4	$54.56	4.777%	$57.1663	$57.17	$57.15	$57.20
Purchase #5	$206.83	7.681%	$222.7166	$222.72	$222.70	$222.70
Purchase #6	$7.27	9.255%	$7.9428	$7.94	$7.95	$7.90
Purchase #7	$138.46	6.784%	$147.8531	$147.85	$147.85	$147.90
7 purchase totals =	$648.51		$692.1741	$692.17	$692.15	$692.20