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	$143.42	13.540%	$162.8391	$162.84	$162.85	$162.80
Purchase #2	$36.34	3.852%	$37.7398	$37.74	$37.75	$37.70
Purchase #3	$215.35	6.663%	$229.6988	$229.70	$229.70	$229.70
Purchase #4	$178.35	4.357%	$186.1207	$186.12	$186.10	$186.10
Purchase #5	$154.29	8.805%	$167.8752	$167.88	$167.90	$167.90
Purchase #6	$128.68	7.329%	$138.111	$138.11	$138.10	$138.10
Purchase #7	$77.30	6.472%	$82.3029	$82.30	$82.30	$82.30
7 purchase totals =	$933.73		$1,004.6875	$1,004.69	$1,004.70	$1,004.60