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	$145.48	4.790%	$152.4485	$152.45	$152.45	$152.40
Purchase #2	$97.27	10.607%	$107.5874	$107.59	$107.60	$107.60
Purchase #3	$64.53	7.152%	$69.1452	$69.15	$69.15	$69.10
Purchase #4	$67.80	6.225%	$72.0206	$72.02	$72.00	$72.00
Purchase #5	$57.72	13.680%	$65.6161	$65.62	$65.60	$65.60
Purchase #6	$65.68	3.699%	$68.1095	$68.11	$68.10	$68.10
Purchase #7	$95.69	5.614%	$101.062	$101.06	$101.05	$101.10
7 purchase totals =	$594.17		$635.9893	$636.00	$635.95	$635.90