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	$49.35	10.560%	$54.5614	$54.56	$54.55	$54.60
Purchase #2	$98.90	6.522%	$105.3503	$105.35	$105.35	$105.40
Purchase #3	$183.63	5.797%	$194.275	$194.28	$194.30	$194.30
Purchase #4	$183.40	9.233%	$200.3333	$200.33	$200.35	$200.30
Purchase #5	$167.91	13.374%	$190.3663	$190.37	$190.35	$190.40
Purchase #6	$132.31	11.461%	$147.474	$147.47	$147.45	$147.50
Purchase #7	$178.41	7.247%	$191.3394	$191.34	$191.35	$191.30
7 purchase totals =	$993.91		$1,083.6997	$1,083.70	$1,083.70	$1,083.80