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	$13.44	4.572%	$14.0545	$14.05	$14.05	$14.10
Purchase #2	$79.42	12.720%	$89.5222	$89.52	$89.50	$89.50
Purchase #3	$95.47	6.751%	$101.9152	$101.92	$101.90	$101.90
Purchase #4	$156.59	8.216%	$169.4554	$169.46	$169.45	$169.50
Purchase #5	$49.27	6.172%	$52.3109	$52.31	$52.30	$52.30
Purchase #6	$167.60	12.515%	$188.5751	$188.58	$188.60	$188.60
Purchase #7	$19.61	4.639%	$20.5197	$20.52	$20.50	$20.50
7 purchase totals =	$581.40		$636.3530	$636.36	$636.30	$636.40