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	$147.43	6.392%	$156.8537	$156.85	$156.85	$156.90
Purchase #2	$140.78	7.550%	$151.4089	$151.41	$151.40	$151.40
Purchase #3	$158.29	6.476%	$168.5409	$168.54	$168.55	$168.50
Purchase #4	$187.78	3.177%	$193.7458	$193.75	$193.75	$193.70
Purchase #5	$18.38	3.372%	$18.9998	$19.00	$19.00	$19.00
Purchase #6	$51.42	13.240%	$58.228	$58.23	$58.25	$58.20
Purchase #7	$238.47	10.851%	$264.3464	$264.35	$264.35	$264.30
7 purchase totals =	$942.55		$1,012.1235	$1,012.13	$1,012.15	$1,012.00