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	$114.91	4.109%	$119.6317	$119.63	$119.65	$119.60
Purchase #2	$81.26	10.571%	$89.85	$89.85	$89.85	$89.90
Purchase #3	$223.27	9.229%	$243.8756	$243.88	$243.90	$243.90
Purchase #4	$207.35	6.429%	$220.6805	$220.68	$220.70	$220.70
Purchase #5	$158.86	8.498%	$172.3599	$172.36	$172.35	$172.40
Purchase #6	$243.56	3.113%	$251.142	$251.14	$251.15	$251.10
Purchase #7	$173.80	6.139%	$184.4696	$184.47	$184.45	$184.50
7 purchase totals =	$1,203.01		$1,282.0093	$1,282.01	$1,282.05	$1,282.10