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	$107.95	9.404%	$118.1016	$118.10	$118.10	$118.10
Purchase #2	$71.75	11.823%	$80.233	$80.23	$80.25	$80.20
Purchase #3	$215.76	6.394%	$229.5557	$229.56	$229.55	$229.60
Purchase #4	$182.53	7.210%	$195.6904	$195.69	$195.70	$195.70
Purchase #5	$159.80	3.816%	$165.898	$165.90	$165.90	$165.90
Purchase #6	$168.34	10.194%	$185.5006	$185.50	$185.50	$185.50
Purchase #7	$145.78	6.582%	$155.3752	$155.38	$155.40	$155.40
7 purchase totals =	$1,051.91		$1,130.3545	$1,130.36	$1,130.40	$1,130.40