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	$179.36	3.633%	$185.8761	$185.88	$185.90	$185.90
Purchase #2	$165.44	13.583%	$187.9117	$187.91	$187.90	$187.90
Purchase #3	$214.30	13.650%	$243.552	$243.55	$243.55	$243.60
Purchase #4	$166.32	12.514%	$187.1333	$187.13	$187.15	$187.10
Purchase #5	$85.84	7.350%	$92.1492	$92.15	$92.15	$92.10
Purchase #6	$123.84	11.131%	$137.6246	$137.62	$137.60	$137.60
Purchase #7	$70.34	11.621%	$78.5142	$78.51	$78.50	$78.50
7 purchase totals =	$1,005.44		$1,112.7611	$1,112.75	$1,112.75	$1,112.70