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	$183.86	4.187%	$191.5582	$191.56	$191.55	$191.60
Purchase #2	$250.99	9.671%	$275.2632	$275.26	$275.25	$275.30
Purchase #3	$116.26	12.196%	$130.4391	$130.44	$130.45	$130.40
Purchase #4	$37.38	13.343%	$42.3676	$42.37	$42.35	$42.40
Purchase #5	$71.87	12.782%	$81.0564	$81.06	$81.05	$81.10
Purchase #6	$115.70	12.841%	$130.557	$130.56	$130.55	$130.60
Purchase #7	$229.58	5.372%	$241.913	$241.91	$241.90	$241.90
7 purchase totals =	$1,005.64		$1,093.1545	$1,093.16	$1,093.10	$1,093.30