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	$96.74	8.185%	$104.6582	$104.66	$104.65	$104.70
Purchase #2	$112.44	6.193%	$119.4034	$119.40	$119.40	$119.40
Purchase #3	$70.26	9.681%	$77.0619	$77.06	$77.05	$77.10
Purchase #4	$88.30	3.551%	$91.4355	$91.44	$91.45	$91.40
Purchase #5	$65.74	8.854%	$71.5606	$71.56	$71.55	$71.60
Purchase #6	$30.27	6.214%	$32.151	$32.15	$32.15	$32.20
Purchase #7	$188.90	4.193%	$196.8206	$196.82	$196.80	$196.80
7 purchase totals =	$652.65		$693.0912	$693.09	$693.05	$693.20