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	$193.53	8.138%	$209.2795	$209.28	$209.30	$209.30
Purchase #2	$250.48	5.647%	$264.6246	$264.62	$264.60	$264.60
Purchase #3	$244.45	4.475%	$255.3891	$255.39	$255.40	$255.40
Purchase #4	$129.59	3.268%	$133.825	$133.83	$133.85	$133.80
Purchase #5	$59.38	9.608%	$65.0852	$65.09	$65.10	$65.10
Purchase #6	$229.70	3.719%	$238.2425	$238.24	$238.25	$238.20
Purchase #7	$203.64	5.807%	$215.4654	$215.47	$215.45	$215.50
7 purchase totals =	$1,310.77		$1,381.9113	$1,381.92	$1,381.95	$1,381.90