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	$154.85	7.533%	$166.5149	$166.51	$166.50	$166.50
Purchase #2	$128.94	3.445%	$133.382	$133.38	$133.40	$133.40
Purchase #3	$139.53	8.763%	$151.757	$151.76	$151.75	$151.80
Purchase #4	$235.28	11.764%	$262.9583	$262.96	$262.95	$263.00
Purchase #5	$75.26	9.107%	$82.1139	$82.11	$82.10	$82.10
Purchase #6	$167.92	9.150%	$183.2847	$183.28	$183.30	$183.30
Purchase #7	$90.72	9.614%	$99.4418	$99.44	$99.45	$99.40
7 purchase totals =	$992.50		$1,079.4526	$1,079.44	$1,079.45	$1,079.50