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	$161.97	3.613%	$167.822	$167.82	$167.80	$167.80
Purchase #2	$22.45	5.531%	$23.6917	$23.69	$23.70	$23.70
Purchase #3	$25.59	11.112%	$28.4336	$28.43	$28.45	$28.40
Purchase #4	$147.36	7.487%	$158.3928	$158.39	$158.40	$158.40
Purchase #5	$215.31	8.627%	$233.8848	$233.88	$233.90	$233.90
Purchase #6	$69.65	11.767%	$77.8457	$77.85	$77.85	$77.80
Purchase #7	$54.86	8.242%	$59.3816	$59.38	$59.40	$59.40
7 purchase totals =	$697.19		$749.4522	$749.44	$749.50	$749.40