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	$164.90	10.331%	$181.9358	$181.94	$181.95	$181.90
Purchase #2	$36.57	3.290%	$37.7732	$37.77	$37.75	$37.80
Purchase #3	$243.98	11.696%	$272.5159	$272.52	$272.50	$272.50
Purchase #4	$12.86	9.236%	$14.0477	$14.05	$14.05	$14.00
Purchase #5	$199.88	9.704%	$219.2764	$219.28	$219.30	$219.30
Purchase #6	$152.33	8.637%	$165.4867	$165.49	$165.50	$165.50
Purchase #7	$73.86	6.380%	$78.5723	$78.57	$78.55	$78.60
7 purchase totals =	$884.38		$969.6080	$969.62	$969.60	$969.60