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	$232.59	13.676%	$264.399	$264.40	$264.40	$264.40
Purchase #2	$27.39	6.298%	$29.115	$29.12	$29.10	$29.10
Purchase #3	$217.54	12.729%	$245.2307	$245.23	$245.25	$245.20
Purchase #4	$93.80	6.497%	$99.8942	$99.89	$99.90	$99.90
Purchase #5	$245.39	13.633%	$278.844	$278.84	$278.85	$278.80
Purchase #6	$113.90	8.422%	$123.4927	$123.49	$123.50	$123.50
Purchase #7	$8.56	7.478%	$9.2001	$9.20	$9.20	$9.20
7 purchase totals =	$939.17		$1,050.1757	$1,050.17	$1,050.20	$1,050.10