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	$72.79	7.771%	$78.4465	$78.45	$78.45	$78.40
Purchase #2	$93.39	4.596%	$97.6822	$97.68	$97.70	$97.70
Purchase #3	$88.32	9.327%	$96.5576	$96.56	$96.55	$96.60
Purchase #4	$230.32	3.446%	$238.2568	$238.26	$238.25	$238.30
Purchase #5	$222.87	4.653%	$233.2401	$233.24	$233.25	$233.20
Purchase #6	$158.36	6.375%	$168.4555	$168.46	$168.45	$168.50
Purchase #7	$110.37	9.490%	$120.8441	$120.84	$120.85	$120.80
7 purchase totals =	$976.42		$1,033.4828	$1,033.49	$1,033.50	$1,033.50