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	$150.68	6.608%	$160.6369	$160.64	$160.65	$160.60
Purchase #2	$47.80	13.606%	$54.3037	$54.30	$54.30	$54.30
Purchase #3	$184.41	5.661%	$194.8495	$194.85	$194.85	$194.80
Purchase #4	$146.71	3.740%	$152.197	$152.20	$152.20	$152.20
Purchase #5	$70.28	11.466%	$78.3383	$78.34	$78.35	$78.30
Purchase #6	$181.27	13.643%	$206.0007	$206.00	$206.00	$206.00
Purchase #7	$159.37	3.242%	$164.5368	$164.54	$164.55	$164.50
7 purchase totals =	$940.52		$1,010.8629	$1,010.87	$1,010.90	$1,010.70