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	$220.70	10.253%	$243.3284	$243.33	$243.35	$243.30
Purchase #2	$34.72	6.656%	$37.031	$37.03	$37.05	$37.00
Purchase #3	$83.27	3.562%	$86.2361	$86.24	$86.25	$86.20
Purchase #4	$245.49	10.289%	$270.7485	$270.75	$270.75	$270.70
Purchase #5	$121.32	4.686%	$127.0051	$127.01	$127.00	$127.00
Purchase #6	$169.44	13.256%	$191.901	$191.90	$191.90	$191.90
Purchase #7	$11.92	12.219%	$13.3765	$13.38	$13.40	$13.40
7 purchase totals =	$886.86		$969.6266	$969.64	$969.70	$969.50