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	$95.89	4.871%	$100.5608	$100.56	$100.55	$100.60
Purchase #2	$209.68	6.259%	$222.8039	$222.80	$222.80	$222.80
Purchase #3	$71.54	3.255%	$73.8686	$73.87	$73.85	$73.90
Purchase #4	$136.94	5.183%	$144.0376	$144.04	$144.05	$144.00
Purchase #5	$134.28	4.241%	$139.9748	$139.97	$139.95	$140.00
Purchase #6	$240.76	11.693%	$268.9121	$268.91	$268.90	$268.90
Purchase #7	$130.79	10.655%	$144.7257	$144.73	$144.75	$144.70
7 purchase totals =	$1,019.88		$1,094.8835	$1,094.88	$1,094.85	$1,094.90