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	$47.61	10.673%	$52.6914	$52.69	$52.70	$52.70
Purchase #2	$94.89	10.646%	$104.992	$104.99	$105.00	$105.00
Purchase #3	$60.41	3.428%	$62.4809	$62.48	$62.50	$62.50
Purchase #4	$135.90	12.174%	$152.4445	$152.44	$152.45	$152.40
Purchase #5	$138.93	6.505%	$147.9674	$147.97	$147.95	$148.00
Purchase #6	$73.86	11.351%	$82.2438	$82.24	$82.25	$82.20
Purchase #7	$174.99	6.139%	$185.7326	$185.73	$185.75	$185.70
7 purchase totals =	$726.59		$788.5526	$788.54	$788.60	$788.50