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	$97.71	11.687%	$109.1294	$109.13	$109.15	$109.10
Purchase #2	$93.31	4.107%	$97.1422	$97.14	$97.15	$97.10
Purchase #3	$206.27	11.367%	$229.7167	$229.72	$229.70	$229.70
Purchase #4	$145.75	4.444%	$152.2271	$152.23	$152.25	$152.20
Purchase #5	$142.35	7.155%	$152.5351	$152.54	$152.55	$152.50
Purchase #6	$148.79	5.175%	$156.4899	$156.49	$156.50	$156.50
Purchase #7	$133.36	10.315%	$147.1161	$147.12	$147.10	$147.10
7 purchase totals =	$967.54		$1,044.3565	$1,044.37	$1,044.40	$1,044.20