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	$220.28	10.460%	$243.3213	$243.32	$243.30	$243.30
Purchase #2	$103.42	7.503%	$111.1796	$111.18	$111.20	$111.20
Purchase #3	$127.80	6.841%	$136.5428	$136.54	$136.55	$136.50
Purchase #4	$191.76	3.583%	$198.6308	$198.63	$198.65	$198.60
Purchase #5	$84.76	13.255%	$95.9949	$95.99	$96.00	$96.00
Purchase #6	$83.28	9.316%	$91.0384	$91.04	$91.05	$91.00
Purchase #7	$150.43	13.852%	$171.2676	$171.27	$171.25	$171.30
7 purchase totals =	$961.73		$1,047.9754	$1,047.97	$1,048.00	$1,047.90