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	$94.94	9.664%	$104.115	$104.12	$104.10	$104.10
Purchase #2	$94.47	5.289%	$99.4665	$99.47	$99.45	$99.50
Purchase #3	$112.41	13.197%	$127.2447	$127.24	$127.25	$127.20
Purchase #4	$49.64	5.220%	$52.2312	$52.23	$52.25	$52.20
Purchase #5	$57.56	6.820%	$61.4856	$61.49	$61.50	$61.50
Purchase #6	$236.70	5.645%	$250.0617	$250.06	$250.05	$250.10
Purchase #7	$83.57	8.627%	$90.7796	$90.78	$90.80	$90.80
7 purchase totals =	$729.29		$785.3843	$785.39	$785.40	$785.40