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	$185.75	3.287%	$191.8556	$191.86	$191.85	$191.90
Purchase #2	$235.74	3.212%	$243.312	$243.31	$243.30	$243.30
Purchase #3	$7.60	6.176%	$8.0694	$8.07	$8.05	$8.10
Purchase #4	$64.92	13.742%	$73.8413	$73.84	$73.85	$73.80
Purchase #5	$123.65	8.588%	$134.2691	$134.27	$134.25	$134.30
Purchase #6	$171.32	8.331%	$185.5927	$185.59	$185.60	$185.60
Purchase #7	$159.47	7.392%	$171.258	$171.26	$171.25	$171.30
7 purchase totals =	$948.45		$1,008.1981	$1,008.20	$1,008.15	$1,008.30