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	$93.76	10.395%	$103.5064	$103.51	$103.50	$103.50
Purchase #2	$85.30	4.721%	$89.327	$89.33	$89.35	$89.30
Purchase #3	$183.70	11.816%	$205.406	$205.41	$205.40	$205.40
Purchase #4	$127.96	13.428%	$145.1425	$145.14	$145.15	$145.10
Purchase #5	$224.47	12.803%	$253.2089	$253.21	$253.20	$253.20
Purchase #6	$119.48	10.579%	$132.1198	$132.12	$132.10	$132.10
Purchase #7	$159.49	7.785%	$171.9063	$171.91	$171.90	$171.90
7 purchase totals =	$994.16		$1,100.6169	$1,100.63	$1,100.60	$1,100.50