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	$90.48	11.790%	$101.1476	$101.15	$101.15	$101.10
Purchase #2	$247.82	13.756%	$281.9101	$281.91	$281.90	$281.90
Purchase #3	$156.55	8.128%	$169.2744	$169.27	$169.25	$169.30
Purchase #4	$95.27	9.156%	$103.9929	$103.99	$104.00	$104.00
Purchase #5	$67.31	4.158%	$70.1087	$70.11	$70.10	$70.10
Purchase #6	$191.71	6.347%	$203.8778	$203.88	$203.90	$203.90
Purchase #7	$118.77	7.694%	$127.9082	$127.91	$127.90	$127.90
7 purchase totals =	$967.91		$1,058.2197	$1,058.22	$1,058.20	$1,058.20