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	$121.72	6.817%	$130.0177	$130.02	$130.00	$130.00
Purchase #2	$129.75	11.657%	$144.875	$144.88	$144.90	$144.90
Purchase #3	$14.44	6.586%	$15.391	$15.39	$15.40	$15.40
Purchase #4	$250.99	4.673%	$262.7188	$262.72	$262.70	$262.70
Purchase #5	$137.41	9.346%	$150.2523	$150.25	$150.25	$150.30
Purchase #6	$162.33	5.851%	$171.8279	$171.83	$171.85	$171.80
Purchase #7	$227.71	4.729%	$238.4784	$238.48	$238.50	$238.50
7 purchase totals =	$1,044.35		$1,113.5611	$1,113.57	$1,113.60	$1,113.60