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	$59.72	13.507%	$67.7864	$67.79	$67.80	$67.80
Purchase #2	$238.57	12.643%	$268.7324	$268.73	$268.75	$268.70
Purchase #3	$176.72	4.718%	$185.0576	$185.06	$185.05	$185.10
Purchase #4	$205.68	11.827%	$230.0058	$230.01	$230.00	$230.00
Purchase #5	$172.56	5.532%	$182.106	$182.11	$182.10	$182.10
Purchase #6	$160.37	5.654%	$169.4373	$169.44	$169.45	$169.40
Purchase #7	$244.76	4.343%	$255.3899	$255.39	$255.40	$255.40
7 purchase totals =	$1,258.38		$1,358.5154	$1,358.53	$1,358.55	$1,358.50