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	$17.61	8.643%	$19.132	$19.13	$19.15	$19.10
Purchase #2	$104.33	4.548%	$109.0749	$109.07	$109.05	$109.10
Purchase #3	$47.48	6.856%	$50.7352	$50.74	$50.75	$50.70
Purchase #4	$70.32	3.161%	$72.5428	$72.54	$72.55	$72.50
Purchase #5	$111.26	10.658%	$123.1181	$123.12	$123.10	$123.10
Purchase #6	$108.92	6.628%	$116.1392	$116.14	$116.15	$116.10
Purchase #7	$152.69	8.270%	$165.3175	$165.32	$165.30	$165.30
7 purchase totals =	$612.61		$656.0597	$656.06	$656.05	$655.90