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	$73.68	6.370%	$78.3734	$78.37	$78.35	$78.40
Purchase #2	$86.30	10.175%	$95.081	$95.08	$95.10	$95.10
Purchase #3	$189.83	4.580%	$198.5242	$198.52	$198.50	$198.50
Purchase #4	$145.55	11.767%	$162.6769	$162.68	$162.70	$162.70
Purchase #5	$140.82	11.134%	$156.4989	$156.50	$156.50	$156.50
Purchase #6	$235.74	4.316%	$245.9145	$245.91	$245.90	$245.90
Purchase #7	$236.93	6.802%	$253.046	$253.05	$253.05	$253.00
7 purchase totals =	$1,108.85		$1,190.1149	$1,190.11	$1,190.10	$1,190.10