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	$90.34	3.448%	$93.4549	$93.45	$93.45	$93.50
Purchase #2	$113.85	11.604%	$127.0612	$127.06	$127.05	$127.10
Purchase #3	$29.95	7.844%	$32.2993	$32.30	$32.30	$32.30
Purchase #4	$210.54	4.174%	$219.3279	$219.33	$219.35	$219.30
Purchase #5	$222.62	9.161%	$243.0142	$243.01	$243.00	$243.00
Purchase #6	$144.89	5.115%	$152.3011	$152.30	$152.30	$152.30
Purchase #7	$137.87	10.479%	$152.3174	$152.32	$152.30	$152.30
7 purchase totals =	$950.06		$1,019.7760	$1,019.77	$1,019.75	$1,019.80