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	$90.56	11.796%	$101.2425	$101.24	$101.25	$101.20
Purchase #2	$94.27	9.567%	$103.2888	$103.29	$103.30	$103.30
Purchase #3	$220.51	5.796%	$233.2908	$233.29	$233.30	$233.30
Purchase #4	$212.57	12.867%	$239.9214	$239.92	$239.90	$239.90
Purchase #5	$6.94	4.715%	$7.2672	$7.27	$7.25	$7.30
Purchase #6	$205.35	5.396%	$216.4307	$216.43	$216.45	$216.40
Purchase #7	$221.53	10.168%	$244.0552	$244.06	$244.05	$244.10
7 purchase totals =	$1,051.73		$1,145.4966	$1,145.50	$1,145.50	$1,145.50