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	$51.25	3.854%	$53.2252	$53.23	$53.25	$53.20
Purchase #2	$179.66	9.107%	$196.0216	$196.02	$196.00	$196.00
Purchase #3	$120.77	5.118%	$126.951	$126.95	$126.95	$127.00
Purchase #4	$70.45	11.204%	$78.3432	$78.34	$78.35	$78.30
Purchase #5	$145.66	8.247%	$157.6726	$157.67	$157.65	$157.70
Purchase #6	$243.28	13.106%	$275.1643	$275.16	$275.15	$275.20
Purchase #7	$177.81	6.275%	$188.9676	$188.97	$188.95	$189.00
7 purchase totals =	$988.88		$1,076.3455	$1,076.34	$1,076.30	$1,076.40