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	$193.96	6.131%	$205.8517	$205.85	$205.85	$205.90
Purchase #2	$18.54	9.319%	$20.2677	$20.27	$20.25	$20.30
Purchase #3	$181.32	7.174%	$194.3279	$194.33	$194.35	$194.30
Purchase #4	$19.67	9.498%	$21.5383	$21.54	$21.55	$21.50
Purchase #5	$150.69	13.656%	$171.2682	$171.27	$171.25	$171.30
Purchase #6	$241.74	9.430%	$264.5361	$264.54	$264.55	$264.50
Purchase #7	$40.78	10.596%	$45.101	$45.10	$45.10	$45.10
7 purchase totals =	$846.70		$922.8909	$922.90	$922.90	$922.90