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	$90.91	6.187%	$96.5346	$96.53	$96.55	$96.50
Purchase #2	$48.34	9.847%	$53.1	$53.10	$53.10	$53.10
Purchase #3	$149.72	7.226%	$160.5388	$160.54	$160.55	$160.50
Purchase #4	$192.44	13.709%	$218.8216	$218.82	$218.80	$218.80
Purchase #5	$215.49	4.205%	$224.5514	$224.55	$224.55	$224.60
Purchase #6	$175.92	5.236%	$185.1312	$185.13	$185.15	$185.10
Purchase #7	$75.35	6.806%	$80.4783	$80.48	$80.50	$80.50
7 purchase totals =	$948.17		$1,019.1559	$1,019.15	$1,019.20	$1,019.10