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	$181.47	5.431%	$191.3256	$191.33	$191.35	$191.30
Purchase #2	$134.82	11.352%	$150.1248	$150.12	$150.10	$150.10
Purchase #3	$228.46	9.799%	$250.8468	$250.85	$250.85	$250.80
Purchase #4	$205.51	11.141%	$228.4059	$228.41	$228.40	$228.40
Purchase #5	$42.78	7.547%	$46.0086	$46.01	$46.00	$46.00
Purchase #6	$80.43	3.587%	$83.315	$83.32	$83.30	$83.30
Purchase #7	$17.27	5.563%	$18.2307	$18.23	$18.25	$18.20
7 purchase totals =	$890.74		$968.2574	$968.27	$968.25	$968.10