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	$172.56	7.790%	$186.0024	$186.00	$186.00	$186.00
Purchase #2	$77.63	11.276%	$86.3836	$86.38	$86.40	$86.40
Purchase #3	$6.92	4.115%	$7.2048	$7.20	$7.20	$7.20
Purchase #4	$17.48	13.568%	$19.8517	$19.85	$19.85	$19.90
Purchase #5	$20.70	4.407%	$21.6122	$21.61	$21.60	$21.60
Purchase #6	$200.35	10.472%	$221.3307	$221.33	$221.35	$221.30
Purchase #7	$65.76	9.683%	$72.1275	$72.13	$72.15	$72.10
7 purchase totals =	$561.40		$614.5129	$614.50	$614.55	$614.50