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	$58.42	4.593%	$61.1032	$61.10	$61.10	$61.10
Purchase #2	$44.89	12.183%	$50.3589	$50.36	$50.35	$50.40
Purchase #3	$208.54	5.122%	$219.2214	$219.22	$219.20	$219.20
Purchase #4	$238.61	3.772%	$247.6104	$247.61	$247.60	$247.60
Purchase #5	$160.38	13.205%	$181.5582	$181.56	$181.55	$181.60
Purchase #6	$27.34	3.849%	$28.3923	$28.39	$28.40	$28.40
Purchase #7	$147.61	4.372%	$154.0635	$154.06	$154.05	$154.10
7 purchase totals =	$885.79		$942.3079	$942.30	$942.25	$942.40