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	$141.76	4.756%	$148.5021	$148.50	$148.50	$148.50
Purchase #2	$179.27	7.501%	$192.717	$192.72	$192.70	$192.70
Purchase #3	$171.49	4.329%	$178.9138	$178.91	$178.90	$178.90
Purchase #4	$213.50	9.609%	$234.0152	$234.02	$234.00	$234.00
Purchase #5	$56.80	4.374%	$59.2844	$59.28	$59.30	$59.30
Purchase #6	$97.92	12.116%	$109.784	$109.78	$109.80	$109.80
Purchase #7	$216.73	11.800%	$242.3041	$242.30	$242.30	$242.30
7 purchase totals =	$1,077.47		$1,165.5206	$1,165.51	$1,165.50	$1,165.50