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	$112.65	10.323%	$124.2789	$124.28	$124.30	$124.30
Purchase #2	$174.31	11.159%	$193.7613	$193.76	$193.75	$193.80
Purchase #3	$234.81	3.739%	$243.5895	$243.59	$243.60	$243.60
Purchase #4	$52.61	13.800%	$59.8702	$59.87	$59.85	$59.90
Purchase #5	$31.44	6.292%	$33.4182	$33.42	$33.40	$33.40
Purchase #6	$95.82	13.630%	$108.8803	$108.88	$108.90	$108.90
Purchase #7	$244.30	3.494%	$252.8358	$252.84	$252.85	$252.80
7 purchase totals =	$945.94		$1,016.6342	$1,016.64	$1,016.65	$1,016.70