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	$207.62	3.746%	$215.3974	$215.40	$215.40	$215.40
Purchase #2	$91.58	12.696%	$103.207	$103.21	$103.20	$103.20
Purchase #3	$103.42	6.519%	$110.1619	$110.16	$110.15	$110.20
Purchase #4	$181.88	5.349%	$191.6088	$191.61	$191.60	$191.60
Purchase #5	$89.25	11.282%	$99.3192	$99.32	$99.30	$99.30
Purchase #6	$226.43	8.463%	$245.5928	$245.59	$245.60	$245.60
Purchase #7	$106.46	13.116%	$120.4233	$120.42	$120.40	$120.40
7 purchase totals =	$1,006.64		$1,085.7104	$1,085.71	$1,085.65	$1,085.70