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	$192.75	10.114%	$212.2447	$212.24	$212.25	$212.20
Purchase #2	$236.86	10.383%	$261.4532	$261.45	$261.45	$261.50
Purchase #3	$234.63	6.710%	$250.3737	$250.37	$250.35	$250.40
Purchase #4	$79.93	12.350%	$89.8014	$89.80	$89.80	$89.80
Purchase #5	$19.79	8.297%	$21.432	$21.43	$21.45	$21.40
Purchase #6	$176.82	4.253%	$184.3402	$184.34	$184.35	$184.30
Purchase #7	$85.38	13.186%	$96.6382	$96.64	$96.65	$96.60
7 purchase totals =	$1,026.16		$1,116.2834	$1,116.27	$1,116.30	$1,116.20