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	$92.36	7.675%	$99.4486	$99.45	$99.45	$99.40
Purchase #2	$183.68	3.829%	$190.7131	$190.71	$190.70	$190.70
Purchase #3	$136.62	11.452%	$152.2657	$152.27	$152.25	$152.30
Purchase #4	$246.25	3.373%	$254.556	$254.56	$254.55	$254.60
Purchase #5	$132.60	7.293%	$142.2705	$142.27	$142.25	$142.30
Purchase #6	$167.42	9.171%	$182.7741	$182.77	$182.75	$182.80
Purchase #7	$65.53	9.134%	$71.5155	$71.52	$71.50	$71.50
7 purchase totals =	$1,024.46		$1,093.5435	$1,093.55	$1,093.45	$1,093.60