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	$169.75	6.466%	$180.726	$180.73	$180.75	$180.70
Purchase #2	$221.28	3.649%	$229.3545	$229.35	$229.35	$229.40
Purchase #3	$148.50	9.725%	$162.9416	$162.94	$162.95	$162.90
Purchase #4	$81.37	10.489%	$89.9049	$89.90	$89.90	$89.90
Purchase #5	$211.26	6.830%	$225.6891	$225.69	$225.70	$225.70
Purchase #6	$112.31	11.614%	$125.3537	$125.35	$125.35	$125.40
Purchase #7	$171.27	8.239%	$185.3809	$185.38	$185.40	$185.40
7 purchase totals =	$1,115.74		$1,199.3507	$1,199.34	$1,199.40	$1,199.40