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	$142.73	3.834%	$148.2023	$148.20	$148.20	$148.20
Purchase #2	$171.27	8.369%	$185.6036	$185.60	$185.60	$185.60
Purchase #3	$17.60	4.493%	$18.3908	$18.39	$18.40	$18.40
Purchase #4	$244.51	11.782%	$273.3182	$273.32	$273.30	$273.30
Purchase #5	$198.33	4.626%	$207.5047	$207.50	$207.50	$207.50
Purchase #6	$88.71	8.836%	$96.5484	$96.55	$96.55	$96.50
Purchase #7	$175.32	7.444%	$188.3708	$188.37	$188.35	$188.40
7 purchase totals =	$1,038.47		$1,117.9388	$1,117.93	$1,117.90	$1,117.90