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	$162.69	10.183%	$179.2567	$179.26	$179.25	$179.30
Purchase #2	$26.46	3.597%	$27.4118	$27.41	$27.40	$27.40
Purchase #3	$188.57	6.228%	$200.3141	$200.31	$200.30	$200.30
Purchase #4	$122.52	7.556%	$131.7776	$131.78	$131.80	$131.80
Purchase #5	$91.37	5.257%	$96.1733	$96.17	$96.15	$96.20
Purchase #6	$149.79	10.638%	$165.7247	$165.72	$165.70	$165.70
Purchase #7	$234.96	4.382%	$245.2559	$245.26	$245.25	$245.30
7 purchase totals =	$976.36		$1,045.9141	$1,045.91	$1,045.85	$1,046.00