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	$197.61	4.458%	$206.4195	$206.42	$206.40	$206.40
Purchase #2	$103.86	6.470%	$110.5797	$110.58	$110.60	$110.60
Purchase #3	$67.86	5.454%	$71.5611	$71.56	$71.55	$71.60
Purchase #4	$21.88	12.642%	$24.6461	$24.65	$24.65	$24.60
Purchase #5	$54.32	4.459%	$56.7421	$56.74	$56.75	$56.70
Purchase #6	$158.72	3.488%	$164.2562	$164.26	$164.25	$164.30
Purchase #7	$65.47	8.536%	$71.0585	$71.06	$71.05	$71.10
7 purchase totals =	$669.72		$705.2632	$705.27	$705.25	$705.30