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	$88.49	8.842%	$96.3143	$96.31	$96.30	$96.30
Purchase #2	$59.50	9.724%	$65.2858	$65.29	$65.30	$65.30
Purchase #3	$240.27	3.165%	$247.8745	$247.87	$247.85	$247.90
Purchase #4	$82.35	7.585%	$88.5962	$88.60	$88.60	$88.60
Purchase #5	$198.84	5.320%	$209.4183	$209.42	$209.40	$209.40
Purchase #6	$245.48	11.281%	$273.1726	$273.17	$273.15	$273.20
Purchase #7	$99.71	5.456%	$105.1502	$105.15	$105.15	$105.20
7 purchase totals =	$1,014.64		$1,085.8119	$1,085.81	$1,085.75	$1,085.90