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	$240.91	7.566%	$259.1373	$259.14	$259.15	$259.10
Purchase #2	$221.37	10.374%	$244.3349	$244.33	$244.35	$244.30
Purchase #3	$129.40	10.197%	$142.5949	$142.59	$142.60	$142.60
Purchase #4	$51.62	10.673%	$57.1294	$57.13	$57.15	$57.10
Purchase #5	$89.67	7.466%	$96.3648	$96.36	$96.35	$96.40
Purchase #6	$121.80	4.435%	$127.2018	$127.20	$127.20	$127.20
Purchase #7	$155.72	3.171%	$160.6579	$160.66	$160.65	$160.70
7 purchase totals =	$1,010.49		$1,087.4210	$1,087.41	$1,087.45	$1,087.40