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	$108.52	13.473%	$123.1409	$123.14	$123.15	$123.10
Purchase #2	$245.95	9.365%	$268.9832	$268.98	$269.00	$269.00
Purchase #3	$189.68	7.587%	$204.071	$204.07	$204.05	$204.10
Purchase #4	$94.79	10.811%	$105.0377	$105.04	$105.05	$105.00
Purchase #5	$55.89	4.772%	$58.5571	$58.56	$58.55	$58.60
Purchase #6	$158.61	5.570%	$167.4446	$167.44	$167.45	$167.40
Purchase #7	$170.77	7.710%	$183.9364	$183.94	$183.95	$183.90
7 purchase totals =	$1,024.21		$1,111.1709	$1,111.17	$1,111.20	$1,111.10