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	$114.36	11.220%	$127.1912	$127.19	$127.20	$127.20
Purchase #2	$233.60	3.690%	$242.2198	$242.22	$242.20	$242.20
Purchase #3	$90.28	7.292%	$96.8632	$96.86	$96.85	$96.90
Purchase #4	$211.53	5.822%	$223.8453	$223.85	$223.85	$223.80
Purchase #5	$78.80	3.513%	$81.5682	$81.57	$81.55	$81.60
Purchase #6	$170.50	8.610%	$185.1801	$185.18	$185.20	$185.20
Purchase #7	$245.70	7.766%	$264.7811	$264.78	$264.80	$264.80
7 purchase totals =	$1,144.77		$1,221.6489	$1,221.65	$1,221.65	$1,221.70