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	$35.79	3.808%	$37.1529	$37.15	$37.15	$37.20
Purchase #2	$42.53	7.841%	$45.8648	$45.86	$45.85	$45.90
Purchase #3	$91.59	8.802%	$99.6518	$99.65	$99.65	$99.70
Purchase #4	$22.83	9.518%	$25.003	$25.00	$25.00	$25.00
Purchase #5	$72.42	11.481%	$80.7345	$80.73	$80.75	$80.70
Purchase #6	$25.77	6.133%	$27.3505	$27.35	$27.35	$27.40
Purchase #7	$67.88	8.861%	$73.8948	$73.89	$73.90	$73.90
7 purchase totals =	$358.81		$389.6523	$389.63	$389.65	$389.80