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	$226.93	6.104%	$240.7818	$240.78	$240.80	$240.80
Purchase #2	$117.76	6.412%	$125.3108	$125.31	$125.30	$125.30
Purchase #3	$54.72	6.258%	$58.1444	$58.14	$58.15	$58.10
Purchase #4	$119.94	4.232%	$125.0159	$125.02	$125.00	$125.00
Purchase #5	$54.37	10.132%	$59.8788	$59.88	$59.90	$59.90
Purchase #6	$240.61	6.109%	$255.3089	$255.31	$255.30	$255.30
Purchase #7	$228.27	9.758%	$250.5446	$250.54	$250.55	$250.50
7 purchase totals =	$1,042.60		$1,114.9852	$1,114.98	$1,115.00	$1,114.90