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	$155.68	10.524%	$172.0638	$172.06	$172.05	$172.10
Purchase #2	$39.79	7.870%	$42.9215	$42.92	$42.90	$42.90
Purchase #3	$148.38	11.586%	$165.5713	$165.57	$165.55	$165.60
Purchase #4	$138.76	5.445%	$146.3155	$146.32	$146.30	$146.30
Purchase #5	$113.50	10.328%	$125.2223	$125.22	$125.20	$125.20
Purchase #6	$194.65	9.191%	$212.5403	$212.54	$212.55	$212.50
Purchase #7	$166.57	9.426%	$182.2709	$182.27	$182.25	$182.30
7 purchase totals =	$957.33		$1,046.9056	$1,046.90	$1,046.80	$1,046.90