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	$31.60	7.501%	$33.9703	$33.97	$33.95	$34.00
Purchase #2	$229.56	10.826%	$254.4122	$254.41	$254.40	$254.40
Purchase #3	$134.33	13.727%	$152.7695	$152.77	$152.75	$152.80
Purchase #4	$203.25	4.572%	$212.5426	$212.54	$212.55	$212.50
Purchase #5	$219.33	12.345%	$246.4063	$246.41	$246.40	$246.40
Purchase #6	$174.98	7.601%	$188.2802	$188.28	$188.30	$188.30
Purchase #7	$95.72	5.294%	$100.7874	$100.79	$100.80	$100.80
7 purchase totals =	$1,088.77		$1,189.1685	$1,189.17	$1,189.15	$1,189.20