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	$132.64	11.824%	$148.3234	$148.32	$148.30	$148.30
Purchase #2	$244.82	9.479%	$268.0265	$268.03	$268.05	$268.00
Purchase #3	$62.86	11.153%	$69.8708	$69.87	$69.85	$69.90
Purchase #4	$185.71	3.192%	$191.6379	$191.64	$191.65	$191.60
Purchase #5	$242.82	4.730%	$254.3054	$254.31	$254.30	$254.30
Purchase #6	$29.84	13.801%	$33.9582	$33.96	$33.95	$34.00
Purchase #7	$43.92	5.347%	$46.2684	$46.27	$46.25	$46.30
7 purchase totals =	$942.61		$1,012.3906	$1,012.40	$1,012.35	$1,012.40