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	$141.89	13.361%	$160.8479	$160.85	$160.85	$160.80
Purchase #2	$68.77	6.697%	$73.3755	$73.38	$73.40	$73.40
Purchase #3	$12.51	10.110%	$13.7748	$13.77	$13.75	$13.80
Purchase #4	$205.44	13.465%	$233.1025	$233.10	$233.10	$233.10
Purchase #5	$53.28	5.471%	$56.1949	$56.19	$56.20	$56.20
Purchase #6	$64.27	13.428%	$72.9002	$72.90	$72.90	$72.90
Purchase #7	$89.67	3.799%	$93.0766	$93.08	$93.10	$93.10
7 purchase totals =	$635.83		$703.2724	$703.27	$703.30	$703.30