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	$165.82	3.760%	$172.0548	$172.05	$172.05	$172.10
Purchase #2	$225.56	10.589%	$249.4445	$249.44	$249.45	$249.40
Purchase #3	$101.85	7.348%	$109.3339	$109.33	$109.35	$109.30
Purchase #4	$70.62	12.428%	$79.3967	$79.40	$79.40	$79.40
Purchase #5	$22.84	7.405%	$24.5313	$24.53	$24.55	$24.50
Purchase #6	$125.46	13.107%	$141.904	$141.90	$141.90	$141.90
Purchase #7	$113.78	6.239%	$120.8787	$120.88	$120.90	$120.90
7 purchase totals =	$825.93		$897.5439	$897.53	$897.60	$897.50