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	$111.74	12.849%	$126.0975	$126.10	$126.10	$126.10
Purchase #2	$207.75	7.474%	$223.2772	$223.28	$223.30	$223.30
Purchase #3	$6.32	7.824%	$6.8145	$6.81	$6.80	$6.80
Purchase #4	$184.37	6.701%	$196.7246	$196.72	$196.70	$196.70
Purchase #5	$39.39	10.317%	$43.4539	$43.45	$43.45	$43.50
Purchase #6	$205.38	13.802%	$233.7265	$233.73	$233.75	$233.70
Purchase #7	$172.38	11.168%	$191.6314	$191.63	$191.65	$191.60
7 purchase totals =	$927.33		$1,021.7256	$1,021.72	$1,021.75	$1,021.70