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	$62.45	9.766%	$68.5489	$68.55	$68.55	$68.50
Purchase #2	$102.98	8.220%	$111.445	$111.45	$111.45	$111.40
Purchase #3	$185.56	8.135%	$200.6553	$200.66	$200.65	$200.70
Purchase #4	$115.30	11.280%	$128.3058	$128.31	$128.30	$128.30
Purchase #5	$83.67	12.413%	$94.056	$94.06	$94.05	$94.10
Purchase #6	$233.87	10.864%	$259.2776	$259.28	$259.30	$259.30
Purchase #7	$55.89	13.809%	$63.6079	$63.61	$63.60	$63.60
7 purchase totals =	$839.72		$925.8965	$925.92	$925.90	$925.90