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	$49.32	5.648%	$52.1056	$52.11	$52.10	$52.10
Purchase #2	$15.44	10.218%	$17.0177	$17.02	$17.00	$17.00
Purchase #3	$67.28	7.443%	$72.2877	$72.29	$72.30	$72.30
Purchase #4	$43.27	4.714%	$45.3097	$45.31	$45.30	$45.30
Purchase #5	$91.64	3.781%	$95.1049	$95.10	$95.10	$95.10
Purchase #6	$53.95	6.412%	$57.4093	$57.41	$57.40	$57.40
Purchase #7	$206.74	4.637%	$216.3265	$216.33	$216.35	$216.30
7 purchase totals =	$527.64		$555.5614	$555.57	$555.55	$555.50