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	$54.89	11.360%	$61.1255	$61.13	$61.15	$61.10
Purchase #2	$29.88	11.338%	$33.2678	$33.27	$33.25	$33.30
Purchase #3	$156.77	8.757%	$170.4983	$170.50	$170.50	$170.50
Purchase #4	$53.67	12.103%	$60.1657	$60.17	$60.15	$60.20
Purchase #5	$157.37	13.678%	$178.8951	$178.90	$178.90	$178.90
Purchase #6	$92.50	4.137%	$96.3267	$96.33	$96.35	$96.30
Purchase #7	$109.37	4.289%	$114.0609	$114.06	$114.05	$114.10
7 purchase totals =	$654.45		$714.3400	$714.36	$714.35	$714.40